Not impossible mind you (I've got an Alienware 32 QD-OLED monitor mounted to my monitor arm as I type this), just tricky and worth knowing if you plan to mount one of these on your own.
Now with the Alienware 32 QD-OLED AW3225QF in my hands, or rather at my desk ... to the mount with the already attached screw, which had a neat little handle. Then, while the monitor was still ...